An MS accessing a Base Station (BS) and in communication can cause a timing offset and a frequency offset depending on a position change. Thus, the BS adjusts the timing offset and frequency offset of the MS through periodical ranging.
In a periodical ranging mode, if not being allocated UpLink (UL) resources within a driving time of a timer, an MS transmits a periodic ranging code to a BS. That is, only if driving of the timer terminates, the MS transmits the periodical ranging code to the BS for the sake of periodical ranging. Alternatively, if being allocated the UL resources within the driving time of the timer, the MS reactivates the timer.
Thus, if an MS continuously transmits UL data, or transmits UL data before driving of a timer terminates, there is a problem that the MS fails to transmit a periodical ranging code and thus, cannot perform periodical ranging. For example, if a transmission period of a UL transmit power of an MS is shorter than a driving time of a timer for periodical ranging, there is a problem that the MS reactivates the timer whenever transmitting the UL transmit power and thus, cannot perform the periodical ranging.